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Flexible Mining Cables

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  1. Flexible Mining Cables Made for extremes Mining Cables – Owen Barry – Mine Safety – 16/10/2013

  2. From Picture courtesy of NSW T&I Image Library

  3. To Picture courtesy of NSW T&I Image Library

  4. And Picture courtesy of NSW T&I Image Library

  5. From Picture courtesy of NSW T&I Image Library

  6. To Picture courtesy of NSW T&I Image Library

  7. And Picture courtesy of NSW T&I Image Library

  8. Cable damage • Likelihood of cable damage is elevated • Machines are big and mobile • Cables being dragged and pulled • Some are continually reeled • Other large equipment moving in close proximity to cables • Connection to mine earth dependent on integrity of cable

  9. Risk from cable damage • Electrocution • Electric shock • Ignition of gas or dust • Fires • Burns (proximity to arc flash)

  10. Controls to minimise risks- from cable damage • Cable management plans • Training of personnel • Placement of cables • Cable handling equipment • IT supply systems • 1st fault is low energy earth fault • Electrical protection systems • Sensitive earth leakage • Cables constructed to set standards • AS/NZS 1802 • AS/NZS 1972 • AS/NZS 2802

  11. Cable handling – O/Cut

  12. Standards for mining cables • AS/NZS 1802:2003 Electric cables—Reeling and trailing—For underground coal mining • AS/NZS 1972:2006 Electric cables—Underground coal mines—Other than reeling and trailing • AS/NZS 2802:2000 Electric cables—Reeling and trailing—For mining and general use (other than underground coal mining)

  13. Cable design • Earth screened • Damage to earth before another phase • Voltage rated for line to earth, not phase to earth • Function of the IT supply system • Solid construction gives impact resistance • Sheath materials resistant to: • Cuts, abrasions and tears • Water ingress • Chemicals – UV, oils and greases, acids & alkali • Heat

  14. Extreme cable handling Example of poor cable handling.Dragline cables being towed behind a dozer

  15. AS/NZS 1802:2003 Scope • Reeling and trailing electric cables for use in underground coal mines. • Cables used for alternating current supply must be electrically symmetrical. • Specifies construction and dimensional requirements for specific types of cables

  16. Cable constructions – Type 240

  17. Cable constructions – Type 241

  18. AS/NZS 1972:2006 Scope • Specifies the construction of cables for use in underground coal mines other than reeling and trailing cables, ie • Reticulation/feeder cables • Machine cables • Mine shaft winder cables • Generally, does not apply to cables for IS circuits, data, communication and control cables unless specifically covered.

  19. AS/NZS 2802:2003Scope • Intended for: • surface mining, • underground mining (other than coal mining), and • general use, • Allows for two classes of multicore, elastomer insulated and sheathed flexible reeling and trailing cables. • No requirement for symmetrical construction

  20. Cable construction – Type 450

  21. AS/NZS 2802:2003Class 1 cables • Insulated with a high grade ethylene propylene rubber (XR-EP-90) • Permits a reduced radial thickness for the insulation compared with equivalent rated Class 2 cables • Cable sheath is extra-heavy duty (XHD-90-CSP, XHD-90-CPE or XHD-85-PCP) • Designed for slow reeling or trailing applications

  22. AS/NZS 2802:2003Class 2 cables • Insulated using standard R-EP-90 insulation • Sheath material is HD-90-CSP, HD-90-CPE or HD-85-PCP • Greater insulation radial thickness required, providing a more robust cable • Designed for trailing and most reeling applications

  23. Cable constructionFlexibility • Issues affecting flexibility • Insulation materials • Stranding • Length of lay • Bunches • Cores • Screening technique • Sheath thickness • Ability of internal parts to move during flexing and bending

  24. Type 245 cable

  25. Cable constructionComposite screens • Each phase individually screened • Semiconductive layer over insulation • May be elastomer and or tape • For stress relief and potential equalisation • VR < 200 Ωm • Copper and high tenacity yarn • Usually woven • May be helically wound • Screening is also cable earth

  26. Cable constructionElastomer screens • Phases individually screen • Complete assembly collectively screened • Must carry fault current • VR <1 Ωm • 3 interstitial earth conductors embedded in semiconductive elastomer N.B. When crushed, the collective earth screen may separate from the phase conductor

  27. Insulation Voltage Gradient Phase volts Insulation Semi-conductive rubber earth screen Voltage 0 volts Distance – phase conductor to screen

  28. Cable constructionElectrically symmetrical • Cores arranged in geometrically symmetrical pattern to minimise the effects of induced voltage • Important in hazardous zones underground • Minimises sparking between machines • Minimises touch voltages of machines relative to remote earth • shuttle cars have rubber tyres • Mandatory testing for symmetry by cable repair facilities

  29. Future developments • Cable standards presently being revised • A lot of prescriptive elements • 1802 & 2802 will possibly be combined into single standard • Present tests do not adequately assess cable performance • No tests for bending and flexing • No tests for semiconductive individual screen

  30. Future developments Performance based standard • Cable performance outcomes to be defined • Bending and flexing • Tension loads • Aging under elevated operating temperatures • Allow for future requirements • Fibre optics • New insulation materials • New manufacturing techniques • Higher operating voltages

  31. Performance based standard • Performance requirements for each application of cable to be defined: • Draglines • Shovels • Feeder cables – fixed equipment • Continuous miners • Shuttle cars • Monorail systems • Shearer

  32. Performance based standardTests • Type tests to be developed • Verify design achieves required outcomes • Pass/fail criteria to be identified • Routine tests to be developed • Routine tests demonstrate that the production run of cable is the same as the type tested unit • Frequency of sampling • What elements need to be checked • Allowable tolerances from type tested unit

  33. Repair of cables • Presently addressed under AS/NZS 1747 • Will be revised after 1802 & 2802 • Manufacturers will need to identify how repairs will be performed when developing new cable designs • Repair materials • Repair techniques Issue: Mines will need to define element such as stranding and length of lay for compatibility with existing cable fleet

  34. Thank youQuestions